The present invention relates generally to systems for transferring dry free flowing bulk products in the form of powders or granules or the like, and more particularly to such a system employing a novel valving and control arrangement operative to automatically cycle the system between alternate fill and discharge cycles in a highly efficient and economical manner.
Systems for transferring bulk products, and particularly relatively dry flowable particulate or pulverulent materials are generally known. Such systems generally employ a substantially closed vessel or tank having an inlet opening through which the particulate material may be drawn from a source, such as the hold of a ship or a railcar, after which the flowable material is discharged at a discharge outlet for transfer by way of a pneumatic flow line or the like to a different location such as a storage silo. See, for example, U.S. Pat. Nos. 3,372,958 to R. R. Black and 3,861,830 to R. D. Johnson. The systems disclosed in these patents operate on the principle of creating a vacuum or suction within the vessel to effect input loading of flowable particulate or pulverulent product into the vessel or tank until the vessel is substantially full at which time a positive fluid pressure is introduced into the vessel so as to force the material from the discharge outlet into a discharge line in which the material is pneumatically conveyed to a remote storage facility. Such filling and discharge of the vessel is effected automatically in an alternating cyclical manner by means of a valving control arrangement operative to alternately apply suction and pneumatic pressure to the vessel.
While the prior systems have provided generally satisfactory operation, they employ rather complex structural arrangements which add significantly to the costs of such systems and lead to substantial down time in the event of malfunction or maintenance requirements. A more significant disadvantage exhibited by the prior systems, such as disclosed in the aforementioned Johnson patent, is that they rely on timer controls for either one or both of the fill and discharge cycles and thus must be continually monitored and adjusted to accommodate changes in the particular material being transferred, changes in elevation between the transfer system vessel and the storage hold or railcar from which material is drawn, and changes in length of the various lines or conduits through which the material is drawn into the transfer vessel and subsequently discharged.